Among the problems which have existed in the area of oil recovery, has been that of extracting, from a particular oil well, or well within a particular field, a satisfactory percentage of the total amount of the oil and gas within the particular petroleum reservoir.
This problem arises from the fact that, among the presently existing state of the art petroleum methods, none of said methods, which have proven to be otherwise practical, have produced an effective yield capability of more than 50 percent of the oil originally in place. The percentage of recovery which is generally obtainable will depend on such factors as: (1) the physical nature of both the reservoir rock and the oil itself; (2) the care exercised in completing and producing a particular well; and (3) the rate of oil and gas production from the field or reservoir as a whole.
Accordingly, it may be readily appreciated that vast quantities of valuable oil reserves have proven to be inaccessible by reason of various geological and technical factors. Alternatively, even where existent technology has proven adequate, the cost of such technology has proven to be unacceptable.
The prior art has of course witnessed various approaches which have been attempted in order to increase the recovery efficiency of existing oil wells.
For example, U.S. Pat. No. 3,103,975 (1963) entitled Communication Between Wells, held by A. W. Hanson, discloses a general technique directed to the utilization of an electrolyte in order to provide subterranean formations with an electro-chemical treatment which will improve the electrical communication within the various interstices which exist within a normal oil-bearing sedimentary stratum. Through the increase of such electrical communication, generally known as electrical conductivity, a flow of energy can be generated which will have the desired effect of enlarging the area of fracture and, thereby, the effective well or reservoir radius of the recovery area. Said patent to Hanson represents an interesting theoretical approach whose promise has not, as yet, been fully realized.
Also, of pertinence in the prior art in U.S. Pat. No. 3,106,244 (1963), entitled Process for Producing Oil Shale in Situ by Electro-carbonization, held by E. W. Parker. Said patent is representative of on-going technical efforts which have been exerted in the area of extracting oil from shale deposits through the appropriate application of electrical energy. As such, said patent represents another step in the development of the technology which has led to the present invention effort.
The use of electrical energy as a thermal source within petroleum strata is discussed in U.S. Pat. No. 3,149,672 (1964), entitled Method and Apparatus for Electrical Heating of Oil-Bearing Formations, held by J. Orkiszewski et al. An allied disclosure appears in U.S. Pat. No. 3,862,662, entitled Method and Apparatus for Electrical Heating of Hydro-Carbonaceous Formations, held by L. R. Kern.
Finally, and of close pertinence to the present inventive method, are U.S. Pat. Nos. 3,169,577 (1965) and 3,236,304 (1966), both held by E. Sarapuu. The first of said patents relates to the electro-linking of two wells through the use of impulse voltages on the order of 150 kilovolts. The second of said patents relates to a method for the electrofracing of oil sand formations through perforated casings.
The present inventive method may be viewed as a natural and necessary advancement of the above original but rudimentary methods proposed by the above inventors.